Modular stub shaft assembly for a centrifugal pump

ABSTRACT

An assembly is provided for interconnecting a drive shaft of a motor to an impeller of a pump. The assembly includes a stub shaft having an end with a fastener for connecting the stub shaft to an impeller and an opposite end in the form of a sleeve having an inner diameter defining a cavity. The assembly also includes a motor shaft sleeve having an end received within the cavity of the stub shaft and an opposite end in the form of a sleeve having an inner diameter defining a cavity therein for receiving, engaging and being secured to the drive shaft of the motor. The inner diameter of the sleeve of the motor shaft sleeve is smaller than the inner diameter of the sleeve of the stub shaft. A pump and a method of interconnecting a drive shaft of a motor to an impeller are also provided.

BACKGROUND

Embodiments disclosed herein relate to pumps, and more particularly, to a modular stub shaft assembly for use, for instance, in the assembly of a centrifugal pump.

Centrifugal pumps, for example, are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy may be provided by an electric motor having a drive shaft rotating an impeller within a volute chamber or casing. The fluid enters the pump impeller along or near to the rotating axis of the impeller and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from where it exits. Thus, fluid enters axially through an eye of the casing, is caught up in the impeller blades, and is whirled tangentially and radially outward until it leaves through circumferential parts of the impeller into the diffuser part of the casing. The flow of fluid gains both velocity and pressure while passing through the impeller.

A stub shaft may be used to interconnect the drive shaft of the motor to the impeller. Thus, one end of the stub shaft is secured to the drive shaft for rotation therewith and an impeller is secured to the opposite end of the stub shaft. Since the stub shaft extends into the volute chamber to position the impeller therein, a fluid-tight seal is formed about a portion of the stub shaft to prevent fluid from leaking out of the chamber where the stub shaft enters the chamber.

In some instances, it may be necessary to change or replace the motor. Since the drive shafts of motors are provided in different sizes, this may also necessitate replacement of the stub shaft.

SUMMARY

According to one aspect of the present invention, an assembly is provided for interconnecting a drive shaft of a motor to an impeller of a pump. The assembly includes a stub shaft that has an end with a fastener for connecting the stub shaft to the impeller and an opposite end in the faun of a sleeve having an inner diameter defining a cavity therein. The assembly also includes a separate motor shaft sleeve that has an end inserted and received within the cavity of the stub shaft and secured thereto and an opposite end in the form of a sleeve having an inner diameter defining a cavity therein for receiving, engaging and being secured to the drive shaft of the motor. The inner diameter of the sleeve of the motor shaft sleeve is smaller than the inner diameter of the sleeve of the stub shaft.

According to another aspect of the present invention, a pump is provided. The pump includes a motor having a drive shaft and a volute chamber containing an impeller. The pump also includes a stub shaft having an end with a fastener connecting the stub shaft to the impeller and an opposite end in the form of a sleeve having an inner diameter defining a cavity therein. The pump further includes a motor shaft sleeve having an end inserted and received within the cavity of the sleeve of the stub shaft and secured thereto and an opposite end in the form of a sleeve having an inner diameter defining a cavity therein for receiving, engaging and being secured to the drive shaft of the motor.

According to a further aspect of the present invention, a method of interconnecting a drive shaft of a motor to an impeller of a pump is provided. The method includes a step of selecting a motor shaft sleeve from a set of motor shaft sleeves in which motor shaft sleeves having different inner diameters are provided such that a motor shaft sleeve having an inner diameter that is able to receive and closely matches an outer diameter of the drive shaft of the motor is selected. The method also includes inserting an end of the motor shaft sleeve within a cavity of a sleeve of a stub shaft that is secured to the impeller of the pump within a sealed volute chamber. Further, the method includes securing the motor shaft sleeve to the stub shaft and securing an opposite end of the motor shaft sleeve to the drive shaft of the motor.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the embodiments disclosed herein should become apparent from the following description when taken in conjunction with the accompanying drawings.

FIG. 1 is a perspective view of an exemplary centrifugal pump.

FIG. 2 is an exploded perspective view of a centrifugal pump in accordance to an embodiment.

FIG. 3 is a perspective view of a modular shaft/sleeve assembly of the stub shaft used in the centrifugal pump shown in FIG. 2.

FIG. 4 is an enlarged view of the modular shaft/sleeve assembly shown in FIG. 3.

FIG. 5 is a perspective view showing the modular shaft/sleeve assembly including a set of three different motor shaft sleeves each having a different motor sleeve inner diameter according to an embodiment.

DETAILED DESCRIPTION

For simplicity and illustrative purposes, the principles of the embodiments are described by referring mainly to examples thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. It will be apparent however, to one of ordinary skill in the art, that the embodiments may be practiced without limitation to these specific details. In some instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the embodiments.

FIG. 1 shows an exemplary embodiment of a pump 10. Pump 10 is a centrifugal pump having an electric motor 12, an adapter section 14, and a volute chamber 16. In FIG. 1, the motor 12 is secured to support legs 18 and interconnects to the volute chamber 16 via the adapter section 14. The volute chamber 16 forms part of a fluid path for a liquid. The liquid enters the volute chamber 16 via piping (not shown) connected to the central inlet 20 and exits the volute chamber 16 via the outlet 22 which interconnects to additional piping (not shown).

An impeller is located within the volute chamber 16 and is rotated via rotational movement of the drive shaft of the motor. Thus, the fluid enters the pump impeller along or near to the rotating axis of the impeller and is accelerated by the impeller, flowing tangentially and radially outward as shown by the arrows “A” in FIG. 1 into the volute chamber 16 until the fluid exits the volute chamber 16 via outlet 22. The flow of fluid gains both velocity and pressure while passing through the impeller.

A centrifugal pump 24 is shown in FIG. 2. Centrifugal pump 24 operates in a similar manner as pump 10 discussed above. Thus, pump 24 includes a motor 26 having a drive shaft 28, a sealed volute chamber 30 having an inlet 32, impeller 34, and outlet 36, and an adapter section 38 which interconnects the drive shaft 28 of the motor 26 to the impeller 34. Unlike a conventional pump, the pump 24 includes a modular pump shaft/sleeve assembly 36 that interconnects the drive shaft 28 of the motor 26 to the impeller 34 within the volute chamber 30.

The adapter section 38 includes a modular pump shaft/sleeve assembly 40 as shown in FIG. 3. The assembly 40 comprises a stub shaft 42 and a motor shaft sleeve 44. The stub shaft 42 has a distal end 46 (distal from the perspective of the drive shaft 28 of the motor 26) shown in the form a threaded bolt 48. The purpose of the distal end 46 is to secure the stub shaft 42 to the impeller 34. While a threaded bolt 48 is shown in FIG. 3 (i.e., for being secured to a complementary nut), any type of fastener or retainer may be used to connect the distal end 46 of the stub shaft 42 to the impeller 34.

The stub shaft 42 also includes a proximal end 50 (proximal from the perspective of the drive shaft 28 of the motor 26). As shown in FIG. 3, the proximal end 50 may be in the form of a hollow sleeve 52 having a pre-determined inner diameter and providing an internal cavity 54 which may be substantially cylindrical. The purpose of the sleeve 52 of the stub shaft 42 is to receive and be secured to the separate motor shaft sleeve 44.

The motor shaft sleeve 44 also has distal and proximal ends, 56 and 58, respectively (i.e., distal and proximal relative to the drive shaft 28 of the motor 26). The outer diameter of the distal end 56 of the motor shaft sleeve 44 is sized to fit within and substantially fill the internal cavity 54 of the stub shaft 42. The outer diameter of the proximal end 58 of the motor shaft sleeve 44 substantially matches that of the inner diameter of the sleeve 52 of the stub shaft 42. Thus, when the distal end 56 of the motor shaft sleeve 44 is inserted into and received within the stub shaft 42, the proximal end 58 of the motor shaft sleeve 44 abuts against and is aligned with the sleeve 52 of the stub shaft 42.

In the inserted condition discussed above, the motor shaft sleeve 44 is prevented from rotation relative to the stub shaft 42. Accordingly, as best shown in FIG. 4, the sleeve 52 of the stub shaft 42 is provided with keyways or grooves 60 cut into the inner diameter of the sleeve 52 and longitudinally therein. In the illustrated embodiment, there is a pair of opposed keyways 60; however, more or less may be utilized. Complementary keyways or grooves 62 are formed in the outer diameter of the distal end 56 of the motor shaft sleeve 44 that can be aligned with the keyways 60 of the stub shaft 42. Thus, feather keys 64, which may be elongate bars of solid metal, may be inserted within the keyways 62 of the motor shaft sleeve 44 such that, when the motor shaft sleeve 44 is inserted within the stub shaft 42, the feather keys 64 align with and extend within the keyways 60 of the stub shaft 42. This assembly prevents rotation of the motor shaft sleeve 44 relative to the stub shaft 42 and properly aligns one or more bores 66 formed in the distal end 56 of the motor shaft sleeve 44 with one or more threaded bores 68 formed in the sleeve 52 of the stub shaft 42. In this manner, dog point set screws or like fasteners 70 may be used to positively secure and lock the motor shaft sleeve 44 to the stub shaft 42 and prevent relative rotation therebetween. Of course, other types of fasteners may be used to align and securely lock the motor shaft sleeve 44 to the stub shaft 42.

The proximal end 58 of the motor shaft sleeve 44 includes a sleeve 72 having an inner diameter of a predetermined size defining a cavity therein for accommodating a predetermined-sized drive shaft of a motor. One or more longitudinally-extending open slots 74 may be formed in the proximal end 58 of the motor shaft drive 44 to enable slight expansion or contraction of the inner diameter to ensure that the proximal end 58 of the motor shaft sleeve 44 may be tightly clamped and secured to and about the drive shaft of the motor. If multiple slots 74 are used, the sleeve 72 is provided as a bifurcated sleeve with multiple bifurcated sections.

Thus, one or more socket head cap screws or like fasteners 76 may be applied to the proximal end 58 of the motor shaft sleeve 44 to reduce the size of the slot(s) 74 so that the proximal end 58 of the motor shaft sleeve 44 tightly engages and clamps onto the drive shaft of the motor without slippage. In this manner, rotation of the drive shaft rotates the motor shaft sleeve 44, stub shaft 42 and impeller 34 as a single integral unit. In the assembled condition, none of these components can rotate without the other components rotating at the same speed of rotation.

As stated above, different motors may have drive shafts of different sizes. Accordingly, as shown in FIG. 5, the modular pump shaft/sleeve assembly 40 may be provided with a set of motor shaft sleeves, 44 a, 44 b and 44 c, each having proximal ends with different inner diameters. For instance, compare inner diameters 78, 80 and 82 of the motor shaft sleeves, 44 a, 44 b and 44 c, respectively. Accordingly, an appropriately-sized motor shaft sleeve can be selected from the set of motor shaft sleeves, 44 a, 44 b and 44 c. For instance, a motor shaft sleeve that can receive and closely matches the outer diameter of the drive shaft of the motor can be selected.

An advantage of the above assembly is that, when a motor requires replacement with a new motor having a different sized drive shaft, the stub shaft 38 may remain while only the motor shaft sleeve 40 is removed and then replaced with a different motor shaft sleeve.

For instance, a method of interconnecting a drive shaft of a motor to an impeller of a pump may comprise the step of selecting a motor shaft sleeve from a set of motor shaft sleeves in which motor shaft sleeves having different inner diameters are provided. Thus, a motor shaft sleeve having an inner diameter that is able to receive and closely matches an outer diameter of the drive shaft of the motor may be selected. The method may also include the step of inserting an end of the motor shaft sleeve within a cavity of a sleeve of a stub shaft. Thereafter, the motor shaft sleeve may be secured to the stub shaft and an opposite end of the motor shaft sleeve may be secured to the drive shaft of the motor.

The method may include positioning a feather key in a keyway formed in an outer diameter of the end of the motor shaft sleeve and aligning the keyway of the motor shaft sleeve with a keyway formed in an inner diameter of the sleeve of the stub shaft such that the feather key is contained within the keyways and prevents relative rotation between the stub shaft and the motor shaft sleeve. Thereafter, a fastener maybe secured within a bore extending radially through the sleeve of the stub shaft and a bore formed in an outer diameter of the end of the motor shaft sleeve to lock the motor shaft sleeve to the stub shaft.

The method may further include a step of securing a bifurcated end of the motor shaft sleeve to the drive shaft of the motor by tightening at least one fastener to thereby compress bifurcated sections of the motor shaft sleeve into tight engagement with the drive shaft of the motor.

The above referenced stub shaft and motor shaft sleeve may be made of stainless steel or other material that resists chipping and rust.

The above description illustrates various embodiments along with examples of how aspects of particular embodiments may be implemented, and are presented to illustrate the flexibility and advantages of particular embodiments as defined by the following claims, and should not be deemed to be the only embodiments. One of ordinary skill in the art will appreciate that based on the above disclosure and the following claims, other arrangements, embodiments, implementations and equivalents may be employed without departing from the scope hereof as defined by the claims. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued. 

We claim:
 1. An assembly for interconnecting a drive shaft of a motor to an impeller of a centrifugal pump, comprising: a stub shaft having an end with a fastener for connecting the stub shaft to an impeller and an opposite end in the form of a sleeve having an inner diameter defining a cavity therein; and a motor shaft sleeve having an end inserted and received within said cavity of said sleeve of said stub shaft and secured thereto and an opposite end in the form of a sleeve having an inner diameter defining a cavity therein for receiving, engaging and being secured to a drive shaft of a motor, said inner diameter of said sleeve of the said motor shaft sleeve being smaller than said inner diameter of said sleeve of said stub shaft.
 2. The assembly according to claim 1, wherein said sleeve of said stub shaft includes a keyway formed in the inner diameter of the sleeve of the stub shaft, wherein said end of the motor shaft sleeve inserted within said sleeve of said stub shaft includes a keyway formed in an outer diameter thereof such that the keyways of the stub shaft and motor shaft sleeve are aligned, and wherein a separate feather key is contained within said aligned keyways thereby preventing relative rotation between the stub shaft and the motor shaft sleeve.
 3. The assembly according to claim 2, wherein said keyways extend longitudinally on said stub shaft and aid motor shaft sleeve, and wherein said feather key is an elongate metal bar.
 4. The assembly according to claim 2, wherein said sleeve of said stub shaft includes a bore extending radially through the sleeve of the stub shaft, wherein said end of the motor shaft sleeve inserted within said sleeve of said stub shaft includes a bore formed in an outer diameter thereof, and wherein said bores of said stub shaft and said motor shaft sleeve are aligned and contain therein a fastener for securing said motor shaft sleeve to said stub shaft.
 5. The assembly according to claim 4, wherein said bore extending through said sleeve of said stub shaft is a threaded bore and said fastener within said bore is a dog point set screw or other fastener type.
 6. The assembly according to claim 4, wherein said sleeve of said motor shaft sleeve has at least one longitudinally-extending open slot formed therein.
 7. The assembly according to claim 6, further comprising a fastener that extends through said sleeve of said motor shaft sleeve and said slot for tightly securing said sleeve of said motor shaft sleeve to the drive shaft of the motor.
 8. The assembly according to claim 4, wherein said sleeve of said motor shaft sleeve has multiple longitudinally-extending slots thereby forming a bifurcated sleeve and wherein said bifurcated sleeve of said motor shaft sleeve includes multiple fasteners for compressing bifurcated sections of said motor shaft sleeve into tight engagement with the drive shaft of the motor.
 9. The assembly according to claim 1, wherein said sleeve of said stub shaft includes a bore extending radially through the sleeve of the stub shaft, wherein said end of the motor shaft sleeve inserted within said sleeve of said stub shaft includes a bore formed in an outer diameter thereof, and wherein said bores of said stub shaft and said motor shaft sleeve are aligned and contain therein a fastener for securing said motor shaft sleeve to said stub shaft.
 10. The assembly according to claim 1, wherein said sleeve of said motor shaft sleeve has at least one longitudinally-extending open slot formed therein and a fastener that extends through said sleeve of said motor shaft sleeve and said slot for tightly securing said sleeve of said motor shaft sleeve to the drive shaft of the motor.
 11. The assembly according to claim 1, wherein said sleeve of said motor shaft sleeve has multiple longitudinally-extending slots thereby forming a bifurcated sleeve and wherein said bifurcated sleeve of said motor shaft sleeve includes multiple fasteners for compressing bifurcated sections of said motor shaft sleeve into tight engagement with the drive shaft of the motor.
 12. The assembly according to claim 1, wherein said stub shaft and said motor shaft sleeve are made of stainless steel.
 13. The assembly according to claim 1, wherein a plurality of motor shaft sleeves are provided each having a different inner diameter defining a different-sized cavity for receiving, engaging and being secured to the drive shaft of the motor such that an appropriately-sized one of said plurality of motor shaft sleeves is selected for interconnecting the drive shaft with said stub shaft.
 14. A pump, comprising: a motor having a drive shaft; a volute chamber (casing) having an impeller; a stub shaft having an end with a fastener connecting the stub shaft to said impeller and an opposite end in the form of a sleeve having an inner diameter defining a cavity therein; and a motor shaft sleeve having an end inserted and received within said cavity of said sleeve of said stub shaft and secured thereto and an opposite end in the form of a sleeve having an inner diameter defining a cavity therein for receiving, engaging and being secured to the drive shaft of the motor, said inner diameter of said sleeve of the said motor shaft sleeve being smaller than said inner diameter of said sleeve of said stub shaft.
 15. The pump according to claim 14, wherein said sleeve of said stub shaft includes a keyway formed in the inner diameter of the sleeve of the stub shaft and said end of the motor shaft sleeve inserted within said sleeve of said stub shaft includes a keyway formed in an outer diameter thereof such that the keyways of the stub shaft and motor shaft sleeve are aligned and contain therein a feather key which prevents relative rotation between the stub shaft and the motor shaft sleeve.
 16. The pump according to claim 15, wherein said sleeve of said stub shaft includes a bore extending radially through the sleeve of the stub shaft and said end of the motor shaft sleeve inserted within said sleeve of said stub shaft having a bore formed in an outer diameter thereof such that the bores of the stub shaft and motor shaft sleeve are aligned and contain therein a fastener for securing the motor shaft sleeve to the stub shaft.
 17. The pump according to claim 16, wherein the sleeve of the motor shaft sleeve has multiple longitudinally-extending slots thereby forming a bifurcated sleeve and wherein said bifurcated sleeve of the motor shaft sleeve includes multiple fasteners for compressing bifurcated sections of the motor shaft sleeve into tight engagement with the drive shaft of the motor.
 18. A method of interconnecting a drive shaft of a motor to an impeller of a pump, comprising the steps of: selecting a motor shaft sleeve from a set of motor shaft sleeves in which motor shaft sleeves having different inner diameters are provided such that a motor shaft sleeve having an inner diameter that is able to receive and closely matches an outer diameter of the drive shaft of the motor is selected; inserting an end of the motor shaft sleeve within a cavity of a sleeve of a stub shaft that is secured to the impeller of the pump within a sealed volute chamber; securing the motor shaft sleeve to the stub shaft; and securing an opposite end of the motor shaft sleeve to the drive shaft of the motor.
 19. The method according to claim 18, wherein said step of inserting the end of the motor shaft sleeve within the cavity of the sleeve of the stub shaft includes positioning a feather key in a keyway formed in an outer diameter of the end of the motor shaft sleeve to be inserted within the stub shaft and aligning the keyway of the motor shaft sleeve with a keyway formed in an inner diameter of the sleeve of the stub shaft such that the feather key is contained within the keyways and prevents relative rotation between the stub shaft and the motor shaft sleeve, and wherein said step of securing the motor shaft sleeve to the stub shaft includes securing a fastener in a bore extending radially through the sleeve of the stub shaft and a bore formed in an outer diameter of the end of the motor shaft sleeve.
 20. The method according to claim 19, wherein the sleeve of the motor shaft sleeve has multiple longitudinally-extending slots thereby forming a bifurcated sleeve, and wherein said step of securing an opposite end of the motor shaft sleeve to the drive shaft of the motor includes tightening at least one fastener to compress bifurcated sections of the motor shaft sleeve into tight engagement with the drive shaft of the motor. 